1. Field of the Invention
The present invention relates to a method of manufacturing 3,3′,4,4′-tetraaminobiphenyl in an effective manner.
2. Background Art
3,3′,4,4′-Tetraaminobiphenyl is an industrially important compound as a raw material for heat resistant polymers, dyes, electronic materials and the like.
Various methods are known as a general manufacturing method for this 3,3′,4,4′-tetraaminobiphenyl. Examples of such methods include a benzidine method (Non-patent Document 1), a biphenyl method (Patent Document 1), a dichlorobenzidine method (Patent Document 2) and a coupling method (Patent Document 3).
(Benzidine Method)
The benzidine method is a classical method of manufacturing 3,3′,4,4′-tetraaminobiphenyl using benzidine as a raw material. A series of several steps are used to synthesize 3,3′,4,4′-tetraaminobiphenyl starting with benzidine (4,4′-diaminobiphenyl).
That is, amino groups in benzidine are first protected by N-acetylation with acetic anhydride, and the resulting acetylated compound is then converted into 3,3′-dinitro-N,N′-diacetylbenzidine by nitration. For example, this nitration is performed with concentrated nitric acid in a mixture of acetic anhydride and acetic acid. 3,3′-Dinitro-N,N′-diacetylbenzidine is treated with a base to remove the acetyl groups and then treated with tin (II) chloride in hydrochloric acid to reduce the nitro groups to yield 3,3′,4,4′-tetraaminobiphenyl (Scheme 1).
(Biphenyl Method)
A method according to Patent Document 1 is known as an improved method of manufacturing 3,3′,4,4′-tetraaminobiphenyl starting with biphenyl as a raw material.
Biphenyl is first diacylated with acetyl chloride under a Friedel-Crafts condition. 4,4′-Diacetylbiphenyl obtained is then treated with hydroxylamine to give a corresponding oxime, which is further converted into N,N′-diacetylbenzidine in the presence of an acid via Beckmann rearrangement. After that, this compound is successively subjected to nitration, deprotection by a base and then reduction of the nitro groups to yield 3,3′,4,4′-tetraaminobiphenyl in the same manner as in the above benzidine method (Scheme 2).
(Dichlorobenzidine Method)
A method according to Patent Document 2 is known as a method directly utilizing a benzidine skeleton. 3,3′-Dichlorobenzidine is treated with ammonia in the presence of a copper catalyst at high temperature (150 to 250° C.) and high pressure (1 to 10 MPa) to yield 3,3′,4,4′-tetraaminobiphenyl (Patent Document 2, Scheme 3).
(Coupling Method)
A method according to Patent Document 3 can be listed as a manufacturing method for 3,3′,4,4′-tetraaminobiphenyl not using the benzidine skeleton as a starting material. This method uses Suzuki's coupling between 4-acetylamino-3-nitrobromobenzene and 4-acetylamino-3-nitrophenyl borate to form the benzidine skeleton, followed by deprotection with a base and reduction of the nitro groups in turn to yield 3,3′,4,4′-tetraaminobiphenyl.
    Patent Document 1: U.S. Pat. No. 5,041,666    Patent Document 2: Japanese Patent Laid-Open Publication No. 2004-161643    Patent Document 3: U.S. Patent Application No. 2005/0215823    Non-patent Document 1: H. Vogel, C. S. Marvel, J., Polym. Sci., 50, 511 (1961)    Non-patent Document 2: I. A. Belenkaya, T. A. Shulla, J. Heterocyclic Chem. 11, 1555-1558 (1989)
However, the above benzidine method has a problem that it involves likelihood of deterioration of working conditions and pollution of the environment, because benzidine, which is the starting material, is a carcinogen.
The above biphenyl method is inefficient, since it requires many steps and heavy use of a stoichiometric quantity of reagents in order to obtain 3,3′,4,4′-tetraaminobiphenyl.
The above dichlorobenzidine method has problems that it requires special attention to deterioration of working conditions and environmental pollution because dichlorobenzidine used is a mutagen, and that it requires special manufacturing facilities because the reaction in the presence of ammonia requires a high temperature and a high pressure.
Moreover, the above-mentioned coupling method additionally requires Grignard reaction and the like to synthesize a borate compound as the starting material for the coupling reaction as well as an expensive palladium catalyst for the coupling reaction. There is thus a problem that it requires steps for catalyst recovery, recycling and the like to complicate the process as a whole and increase a manufacturing cost.
An object of the present invention is thus to provide a manufacturing method capable of efficiently producing 3,3′,4,4′-tetraaminobiphenyl through a smaller number of steps. A starting material different from those used in the conventional manufacturing methods is chosen to eliminate use of highly toxic or carcinogenic substances, thus allowing improvement of working conditions and safer environment.